Nonslip film printer



Oct. 18, 1938.- w KELLOGG 1 2,133,820

NONSLIP FILM PRINTER Filed Sept. 30, 1937 2 Sheets-Sheet l ISnoentor (Ittorneg Zi'tzzz y Oct. 18, 1938. w. KELLOGG 2,133,820

NONSLILP FILM PRINTER Filed e t( 30, 1937 2 Sheets-Sheet 2` Pat entec l Oct. 18,1938 l -2.133,82- NONSLIP FILM PRINTER" Edward vv. K'ellorts Moorestown, N. J., assignor to Radio Corporation oi' Arne'rlca, a corporation ot Delaware.

Application September 30, 1931, Serial No. 166, 9'2- Claiins. (0 1- 271-2.3)

This invention relates to film-feeding mechanism and especially for feeding negative film and positive tiim stock in intimate contact through a contact printer without slippagebetweian the illms 5 and with compensation -for dii'erences in the lengths of the tllms,due to shrinkage or expan- A iilin feeding device of "the general type here involved qwas disclosed and claimed in Bedford Patent 1754,187,-and a printer based on this principle was described in the Journal of the 80- ciety oi -Motion Picture Engineers for August 1934, in an article by 0. N. Batsel, and thpesent invention pertains to a impiovement upon the previous devices. e i

In the apparatus previously described as Just referred to, the-131m travels either in `a free loop or in a loop passingaround a movable idier to the printing point, and the lengthof tliis'loop (of "positive film stock) varies in accordance with the difference in length of the positive and negative The loop length is -not directly controlled .in any manner and the loop occasionally has a" tendency; to become unwieldy -ortodbecome too tight, either oi! whichattects, to a certain extent; the. position of the sound tr`ackprint upon'the Itis apparent to those Skilled inthe art film. that printers`of the type here referred to are used almost exclusively in the printing of sound track from the negative to the positive iilm or in malring duplicate negatives and that they are practically never used in making picture prints.

It will be apparent from an inspection of the patent or article above referred to that the principle of the Bedford printer depends upon the changing of the' angle of incidence ofthe positive iilm stock upon 'the supporting di'tim at the printing point, to produce a effective length of this lin stock at the, printing point in a manner which will.be` hereinaiter de- 10 scribed in greater detail, and to thereby secure compensation for the vatiation in iilm length which ma be due, for example, to shrinkage. In

the present invention I have provided an appa-. ratuswhich .varies this angle of incidence in a verysensitive manner and in which the Variationin loop length required to produce a given change v in'the angle of incidence is a minimum, thereby -retaining the relative position of the sound track on the negative and print. as nearly similar as .30 possible. V

One object oi' myinvention is to provide an improved modiiication of the printer`hi' the said Bedford patent.

Another object oi' my invention is to providea 525) nonslip printer in which a maximum amount of compensation for variations in film length will be secured with a minimum variation in iilm loop dimensions.

Another object oi' my invention is-to provide a 60 printer oi the type described vrlie em the angle variation in the 01' incidence of theillm Will be varied a. aatimum aniountfor a mini um .variation in size of the iilmloop. z 1 c Other andincidentalobjects of my invention will be apparent to those SkillB'd'lli the art from a 5 reading of the following speCitication and trom an inspeetion of the accompanying drawings, in which.' Figure 1 is an elevation of' a commercial form of nonslip printer built in accordance with the 10 .aforiasaid Bedford Patent 1,754,187,

Figure 2 shows th-simplest'embodiment of my invention wherein a single roller is used to increase the angle oi incidence of' the iilm With a given variation in looplength, Figure 3 is a diagram of the forced relations in' the arrangement of Figure a for two positions of the roller 8,

'Figure 4: is-an elevation of a nflodiiied form of printerwlierein the 111m tension rema-inssub- 20 stantially constant iri espective of the `variations in loop length and angle-of incidence, Figure 5'shows a inodiiication of the roller arrangernent of Figure 4:,

Figure 6 shows a ifurther Inodification or Figure g 5 tvherein the linkage between the rollers is slightly modified so that the roller 2.0 moves some- What less than the roller 8, Figure 'shows a form of the Invention wherein the shortening of the loop is'efiected by displac- 30 .ing the sprocket II slightlyto the left.

Figure 8 showsfa moditication of .the apparatus shown in Fig.:'i in`whi'ch the relative length of one oi' the arms is increased tmodifythe resultproduced,

'Figure 9 shows in greater detail a further m odiiication of the apparatus of Figure8 intolving a further slight change in the linkage which' has proven. quite satisfitctory,

Figure 10. shows a' type' oi' toggle spring-and an ro eouiva t -countetweight which may be used inestabli ng abiasing force inthe several types of linkages shown in the other figures,

`liigure 11 Shows the loss of control ofangle at low iilm tensions in the tli'pe oi' scpparatus shown 4.5

inFig. 2, and Figure 12 Shows a modiiication of the apparatus of Flg.-2 wherein an' auxiliary roller is' pro- -vided to compensate for the elasticity of the film.

Referring nowto the drawings, 4 j Figure 1 shows an arrangement oi' rollers which has been employed' in several successful models. The iilm passes around a drum l which is pro- .Viderl witlia' damped ywheel in order that it may run at .uniform speed. Rotation is imparted to thedrum by means of the negative iilm 2 which ls prpelled by sprocket 3. 'I'he unexposed positive iilm or "raw stock" 4 is maintained in con tact with the negative iilm at the printingpoint 5 by means of &. pressure roller G' which is held co 4 ably shrunke 'lli film I3 between the feeding sprocket II and the' printing point 5. 1

The sprockets 3 and' li (which are shown as having the Same number-of teeth) run at the same speed. This is a requirement for printing a synchronous film. In view, however, of the Variations in shrinkage of the films, their linear speed may not be exactly the same even though the number of sprocket holes passed per unit of time is the same. 'I'his difference in linear speed is taken care of without slippage by changes in the angle at which the "raw stoc approaches the printing point 5. If the negative is considerthe linear speed of the negative is below average and therefore its surface speed at point 5 where the two illrns are held in contact is low. Under these conditions, sprocket II tends to feed the "raw stock" through more rapidly than it is carried past the printing point; therefore, excess film .accumulates in the loop l3 between sprocket II and printing point 5. A light spring pressure (not shown) causes the guide roller 8 to move over to the right, under these conditions, to take up thc excess film. The

result is that the "raw stock" now presents 8. concave surface to the negative. As "Lis well known, the material on the concave surface of a bent strip is under compression, and therefore this part of the "raw stock" is shortened. An equilibrium position is thus reached at which the shortening of the "raw stock" surface due to compression is. just sufficient to cause it to move. at the correct speed without slipping. If, on the other hand, the negative has little shrinkage. the drum runs faster and the loop of "raw stoc film tends'to become shorter, the guide roller 8 then moves to the left as illustrated at position B. Under these conditions, the "raw stock" presents a convex surface at the point of contact with the negative and thus the surface becomes stretched until equilibrium is again reached. The mean linear speed of the "raw stock" is the average of that of its stretched and compressed surfaces. Pressure roller 8 may run at any speed and the speed of the "raw stoc surface on this side is' not a. factor in the rate of film travel. Thus, when the guide roller is in position li, the net or center line speed of the raw stock" is greater than that of the concave or propelled surface, while if the guide roller is in position B, the net speed is lessthan that of the propelled surface.

The foregoing discussion of the action of the printer is a rlestatement of what is described in the aforementioned paper by C. N. Batsel.- It is evident that the operator cannot count on predicting the size of the loop IS of "raw stock" between the feeding sprocket II and the printing point 5. Since in ordinary practice, a picture is to be printed on the same him, it is evident that both picture and sound must be printed before the film is developed and therefore no photographically printed marks on the "raw stock" can be utilized for registering the film for accurate synchronism. The operator must thread his raw stock" into the picture printer with. II

' on the negative depends upon the relative positions at the printing point 5 which in turn varies with the length of the film loop I3. There will thus be departures from exact synchronisni, the amounts of such departures being proportional to the difference in the length of "raw stock" loop' 'as the operator threads up the printer and as it actually runs. It is obviously desirable to reduce these Variations 'in synchronism to the smallest practicable amount. This is especially important if a printer of this type is' to be used for 16 mm. film, since in this case a given change in loop length corresponds to a greater time difference and synchronism error than would be the case with 35 mm. prints. i

It is therefore a purpose of my invention to provide an arrangement by which the necessary changes in the angle at which the "raw stock" approaches the printing point of a nonslip printer are produced by a minimum change in loop length.

Figure 2 shows a roller arrangement which has been employed in some model printers, and which slightly reduces the The feeding sprocket II in Figure 2 has been raised with reference to its position in Fig. 1 so that the filin bends only slightly in passing around guide roller 8. An objection to this arrangement is that as the guide roller moves toward the position' B at the left, an excessive degree of min tensionis required to hold the roller in this position. If the roller is to be maintained in contact with the film it must be urged to the right by means of a spring or counterweight (not shown). Figure 3 shows the force relations for positions, A and 1.3 of roller I. Arrow II represents the tension on the film bevariations in loop length.-

tween roller 8 and printing point 5 for position A. Arrow IE is the vector of. the tension between sprocket I'I and guide roller 8. v The resultant IG is seen to be comparable in magnitude with the tension vectors M and I5. The conditions for position B areshown by Vectors I'I, IB and |9- If a spring is applied to the arm 9, the tangential force represented by vector IS must be sornewhat greater than is required of the vector IS owing to the increased tension on the spring, and owing to the obtuse angle between vector I'I and IO, they must be excessively large in order to produce an adequate force IS.

If too much film tensionis required, slipping is change in the direction of pull of the film below the guide roller.

The conditions to be met in providing li roller printer are lost. It la 23. The arms 9 and not be a tight spot.

tension may be understood byreterence to Fig. 4.

In Fig." l an extra movable roller is shown, sup'- v ported on an arm 22 which is pivoted at a. point 21 maintaining rollers 8 and 20 a constant distance apart. Pivot points l0 and 23 are located in line with the printing point 5 and a corresponding point 24 where the illm is held between the sprocket II and the sprocket pad roller 25.

The rollers are supported by this linkage in such a manner that each stretch of uhsupported film is substantially parallel to one of the links in the supporting system. Thus tension between roller 8 and printing point 5 is resisted entirely by a compressional stress in arm 0. Tension between rollers 20 and 8 is resisted entirely by cmpression in link 2! and tension between' point 24 and roller 29 is resisted by compression -in arm 22. There is thus complete equilibrium, and ten- Sion on the iilm has no tendency to cause a displacement of the linkage in any direction.

Neither does the total loop length between points 24 and 25 change at ali by shiiting the position of the rollers. This of course is an impossible condition for operation, since a shortening of the loop would only result in increased tension and would fail to move the rollers as desired. II, however, a slight change is inade from Fig. 4, the required conditions can be readily obtained. For example, if the point at whi.ch the link 2l is pivoted to arm Sis lowered (making the link 2I no longer exactly parallel to the film between rollers 20 and 8) so that roller 20 executes slightly less motion than roller 8, then as the rollers move to the left they will approach each other or the tangent between them shorter.

e iilm loop will cause the rollers "to move to the left as desired. Another expedient consists in retaining the linkage as shown inIE'ig. 4 but moving the sprocket slightly to the left. This causes the film tangent between point 24 and roller 20 to shorten as the rollers move to the left. The iilm must perform mechanical work in displacing the rollers to the left against spring action and it can only perform this mechanical. work if it is under some tension and the loop becomes shorter. The force which the illm under a given tension can exert on the roller to produce displacement may be measured by the amount oi loop Shortening per unit change in roller position. The smaller the change in loop length, the

will become Slightly greater must be the iilm tension to overcome agiven b asing spring tension urging the rollers to the right. The best design is therefore a corndesirable conditions are attained ii' the biasin spring or counterweight' is as light as will be consistent with maintaining the desired loop i'orni 4 The second im and properly guiding the ilgn. b 1 k A th t gn t 8. in age a pcirtant iactor is to so des "the ratio oi roller moveinent to loop shorterling` is substantially constant throughout the required range of movement. This insures that there will The constant of proportionality between roller movement and loop shortening is then adjustedso that at no position will the tension be enough to cause danger of slipping, while at the same'tme the amount of loop shortening is reduced as far as is consistent' with the permissible tension.

It may not be convenient to locate theife'eding sprocket and pad roller as indicatedin Fig. 4.

22 are connected by a link Under these conditions, a shortening of ing eiect or, in

as illustrated in Pig. 4. The arrangement shown in F'ig. 5 is similar to that in Fig. 4: in that the CII stretch of tree lilli! between the guide roller 8 and the printing point 5 is substantially parallel 7 and equal in length to the supporting arm 9. Likewise, the stretch of film between the sprocket II and extra roller 20 is substantially parallel to arm 22. The him between rollers 20 and 8 is not parallel to link 2l but is nevertheless of constant length. As previously pointed out in the discussion oi Fig. *1,-the linkage as shown in Fig. 5, wherein the stretches of free film are parallel to the supporting arms, provides no change inloop length as the rollers are shiited, and therefore tension on the iilm cannot cause the rollers to move. The proportions of the linkage must then b slightly modiiied so that movement of the rollers to the left is accomplished by a small but continuous shortening of the loop.

Fig. 6 shows a modification whereinthe position of the connecting link 2I is' shiited so that roller 20 moves somewhat less than roller 8, and Fig. '7 shows an arrangement wherein theshortening of the-loop is etfected by displatting the sprocket Il slightly to the left. It is not essen- A theiilm is restrained from moveinent;

In general, as one of the arms (for example, arm 9) is lengthened, the Stretch oi' tree film at the. other end of the linkage should be correspondingly lengthened. rangement such as shown in Fig. 8- There are,- however, various modiiications in the proportions of the linkage and positions of the rollers which will give satistactory results.

Pig, 9 shows the arrangement employed ina model which has been built and operated. In this model -proportions were changed and. rollers shitted until an arrangement was found in which, throughout the total required range of movement of guide roller 8, there is a substantially constant ratio of movement of guide roller 8 to change in total loop length. In whatever design is used, it is desirable that the guide roller 8 be placed as close as practicable to the pressure roller I0 so that a small movement of the guide roller causes a' large change in angle of the film. The essential characteristic of the arrangements is thats. second roller is employed; and the two rollers are connected in such a. way that the tendermy of the movement-of the shorten the loop is accompanied bya movement of the second roller 20 which ofi'sets the shortenother words, which by itself .tends .to lengthen the signed that there is throughout the movement of the guide roller a continuous change in the total length of the loop. V 'The enployinent of the second roller has a furthet advantage in that an increased wrap around the guide roller 8 is` provided for all positions oi said guide roller. This is conduciveto more satisfactoryguiding. v 4

As has already been pointed out, it is desliable that the tensio'n on the film be as low as consistent with satisfactory guiding. Practicaldesign considerations may call for modification of the guide roller linkage which give a nonlinear relation between ch'angein loop length and move.- ment of guide roller. Under these conditions, the

'I'his results in an ai'- shaft Orguide roller 8 to loop. The combination is so defilm tension may become objectionably highwhen 

